The present invention relates to an epitaxial silicon single crystal wafer for the manufacture of semiconductor devices with reduced heavy metal impurities present in an epitaxial layer, which impurities degrade reliability of the devices, and a boron-doped silicon single crystal wafer, antimony-doped silicon single crystal wafer, and phosphorus-doped silicon single crystal wafer, which serve as a substrate of the epitaxial wafer, as well as methods for producing them.
Epitaxial silicon single crystal wafers have long been widely used as wafers for the manufacture of discrete semiconductors, bipolar ICs and so forth because of their excellent characteristics. Moreover, as also for MOS LSIs, they are widely used for microprocessor units or flash memory devices because of their excellent soft error and latch up characteristics. Furthermore, in order to improve poor reliability of DRAMs caused by the so-called grown-in defects, which are introduced at the time of the production of silicon single crystals, the need of epitaxial silicon single crystal wafers has been increasingly enlarged.
However, existence of heavy metal impurities on epitaxial silicon single crystal wafers used for such semiconductor devices yields poor characteristics of the semiconductor devices. In particular, as a degree of cleanness required for the latest devices, it is considered that heavy metal impurity concentration must be 1xc3x971010 atoms/cm2 or less, and therefore heavy metal impurities existing on silicon wafers must be reduced as much as possible.
Moreover, in recent researches, it has been pointed out that, even in such epitaxial wafers, influence of the grown-in defects present at surfaces of substrate wafers may be manifested depending on conditions of the epitaxial processes and thickness of the epitaxial layer after the epitaxial growth (Kimura et al., Journal of Japanese Association of Crystal Growth, Vol. 24, No. 5, p.444, 1997).
In particular, N-type substrates doped with antimony (referred to as xe2x80x9cantimony-doped silicon single crystal wafersxe2x80x9d hereinafter) used for low resistance devices have a higher grown-in defect density compared with usual P-type substrates doped with boron (referred to as xe2x80x9cboron-doped silicon single crystal wafersxe2x80x9d hereinafter), because the atomic radius of antimony is larger than that of silicon. Therefore, they have a problem that they suffer from much more significant influence of grown-in defects after the epitaxial growth compared with other substrates.
The importance of gettering techniques has become increasingly higher as one of the techniques for reducing such heavy metal impurities. In the production of the epitaxial silicon single crystal wafers for logic devices, p++ type substrates consisting of boron-doped silicon single crystal wafers having a very high boron concentration expressed in terms of a resistivity of less than 10 mxcexa9xc2x7cm (referred to as xe2x80x9cvery highly boron-doped silicon single crystal waferxe2x80x9d hereinafter) have conventionally been used as substrate wafers for performing epitaxial growth, and they have afforded a higher device yield compared with substrate wafers consisting of p+ type substrates of a high boron concentration that exhibit a resistivity of from 10 mxcexa9xc2x7cm to 100 mxcexa9xc2x7cm (referred to as xe2x80x9chighly boron-doped silicon single crystal waferxe2x80x9d hereinafter). However, the very high boron concentration of the very highly boron-doped silicon single crystal wafer causes a problem that boron impurities in the substrates are once released into the gaseous phase and enter into the epitaxial growth layer again, which is called auto doping.
As countermeasures against such auto doping, for example, the epitaxial growth has been performed under reduced pressure atmosphere, or CVD oxide films have been provided on back surfaces of the substrates. However, there has been a problem that these treatments all lead to reduction of productivity, increase of cost and so forth.
Therefore, it was expected to use highly boron-doped silicon single crystal wafers, which did not require any countermeasure against the auto doping, as the substrate for performing epitaxial growth. However, gettering of the highly boron-doped silicon single crystal wafers having a low oxygen concentration is segregation type gettering attained by boron atoms. Therefore, they suffer from a problem of lower gettering ability for heavy metal impurities of copper, nickel and so forth compared with relaxation type gettering attained by oxide precipitates.
On the other hand, in the production of epitaxial silicon single crystal wafers for CCDs, N-type substrates such as N-type substrate doped with phosphorus (referred to as xe2x80x9cphosphorus-doped silicon single crystal wafersxe2x80x9d hereinafter), and antimony-doped silicon single crystal wafers have conventionally been used as the substrate for performing epitaxial growth. However, these N-type substrates also have a problem that oxygen precipitation is harder to occur in them compared with the boron-doped silicon single crystal wafers. Insufficiency of the gettering ability due to such an insufficient amount of oxygen precipitation in N-type substrates is a detrimental problem for devices sensitive to crystal defects resulting from heavy metal impurities, such as CCDs.
In particular, as for the antimony-doped silicon single crystal wafers, when a silicon single crystal ingot doped with antimony is grown by the Czochralski method, it is extremely difficult to maintain the oxygen concentration in a portion having a high antimony concentration obtained in the latter half of the growth of the single crystal ingot, because of evaporation of antimony oxide. For this reason, the oxygen concentration becomes low, and oxygen precipitation of silicon wafers cut out from such a portion is inhibited. Thus, gettering ability required for the device production cannot be obtained.
However, if it is attempted to obtain, in the antimony-doped silicon single crystal wafers or the phosphorus-doped silicon single crystal wafers, an amount of precipitated oxygen comparable to that obtained in the boron-doped silicon single crystal wafers, there would be caused a problem that prolonged oxygen precipitation heat treatment is required compared with the boron-doped silicon single crystal wafers, which leads to reduced productivity.
Specifically, as for the phosphorus-doped silicon single crystal wafers, for example, performed is a heat treatment called IG heat treatment comprising a first stage heat treatment at a high temperature of 1100xc2x0 C. or higher, a heat treatment for formation of precipitation nuclei at about 600-700xc2x0 C. as the second stage, and a heat treatment for formation of oxide precipitates at about 1000xc2x0 C. as the third stage, for several hours for each stage.
On the other hand, if the oxygen concentration of wafers can be elevated in order to increase the oxygen precipitation of these highly boron-doped silicon single crystal wafers, antimony-doped silicon single crystal wafers and phosphorus-doped silicon single crystal wafers, oxygen precipitation would be promoted, and thus the period required for such heat treatments may be shortened. However, the amount of precipitated oxygen in wafers becomes excessive, and it will cause problems such as deformation of wafers and reduction of wafer strength. Moreover, when an epitaxial layer is formed on the surfaces of these silicon single crystal wafers, there would be caused a problem that harmful defects are generated in the epitaxial layer due to out-diffusion of oxygen impurities, and adversely affect the characteristics of semiconductor devices.
The present invention has been accomplished in order to solve these problems, and its major object is to produce and supply a silicon wafer for epitaxial growth consisting of a highly boron-doped silicon single crystal wafer, an antimony-doped silicon single crystal wafer or a phosphorus-doped silicon single crystal wafer, which allows easy oxygen precipitation and exhibits high gettering ability in spite of its suppressed substrate oxygen concentration that is suppressed in order not to cause problems such as deformation of wafers and reduction of wafer strength, and an epitaxial silicon single crystal wafer in which an epitaxial layer has an extremely low heavy metal impurity concentration and is grown by using the aforementioned wafer as a substrate wafer.
The present invention provides, in order to achieve the aforementioned object, a silicon single crystal wafer doped with a dopant, which has an oxide precipitate or oxidation induced stacking fault density of 1xc3x97109 number/cm3 or higher after a precipitation heat treatment of the silicon single crystal wafer.
Such a silicon single crystal wafer doped with a dopant and having an oxide precipitate or oxidation induced stacking fault density of 1xc3x97109 number/cm3 or higher after a precipitation heat treatment of the silicon single crystal wafer exhibits high gettering effect irrespective of the kind of the dopant. By using this wafer as a substrate wafer of an epitaxial silicon single crystal wafer, an epitaxial silicon single crystal wafer of high quality can be obtained.
The present invention also provides, in order to achieve the aforementioned object, a boron-doped silicon single crystal wafer having a resistivity of from 10 mxcexa9xc2x7cm to 100 mxcexa9xc2x7cm, wherein oxygen concentration in the boron-doped silicon single crystal wafer is 16 ppma according to the standard of JEIDA (Japan Electronic Industry Development Association) or less, and the wafer has an oxide precipitate or oxidation induced stacking fault density of 1xc3x97109 number/cm3 or higher after a precipitation heat treatment.
Such a boron-doped silicon single crystal wafer having a resistivity of from 10 mxcexa9xc2x7cm to 100 mxcexa9xc2x7cm and an oxide precipitate or oxidation induced stacking fault density of 1xc3x97109 number/cm3 or higher after a precipitation heat treatment in spite of the low oxygen concentration in the boron-doped silicon single crystal wafer of 16 ppma or less, in which oxygen is likely to precipitate, exhibits high gettering ability against heavy metal impurities such as those of copper and nickel. In addition, because of the low oxygen concentration in the wafer, deformation of the wafer or insufficient wafer strength can be prevented.
Furthermore, by using such a boron-doped silicon single crystal wafer as a substrate wafer for producing an epitaxial wafer, an epitaxial silicon single crystal wafer with high gettering effect and very low heavy metal impurity concentration in a semiconductor device production layer can be obtained with high productivity without generating harmful defects in the epitaxial layer caused by out-diffusion of oxygen impurities. At the same time, it can solve the problem of the auto doping.
The present invention also provide a boron-doped silicon single crystal wafer having a resistivity of from 10 mxcexa9xc2x7cm to 100 mxcexa9xc2x7cm, which is obtained by slicing a silicon single crystal ingot grown by the Czochralski method with nitrogen doping.
When a boron-doped silicon single crystal wafer having a resistivity of from 10 mxcexa9xc2x7cm to 100 mxcexa9xc2x7cm is one obtained by slicing a silicon single crystal ingot grown by the Czochralski method with nitrogen doping, oxygen precipitation is enhanced by the presence of nitrogen in a bulk portion of the wafer. Thus, the wafer can have high gettering effect even though it has such a low substrate oxygen concentration as will not cause problems such as deformation of the wafer or reduced wafer strength.
Furthermore, by using such a boron-doped silicon single crystal wafer as a substrate wafer for producing an epitaxial wafer, incorporation of impurities into the epitaxial layer due to the auto doping can be prevented, and an epitaxial silicon single crystal wafer that has high gettering effect and very low heavy metal impurity concentration can be obtained with high productivity.
Further, the aforementioned boron-doped silicon single crystal wafer preferably has an oxygen concentration of 16 ppma or less.
With such a low an oxygen concentration of 16 ppma or less, the risk of deformation of the wafer or reduction of wafer strength is further reduced. In addition, the formation of crystal defects in the boron-doped silicon single crystal wafer can be inhibited, and the formation of oxide precipitates in the wafer surface layer can be prevented. Therefore, when an epitaxial layer is formed on the wafer surface, the crystallinity of the epitaxial layer is not adversely affected. On the other hand, because oxygen precipitation is promoted in a bulk portion by the existence of nitrogen, sufficient gettering effect can be obtained in spite of such a low oxygen concentration.
The present invention further provides, in order to achieve the aforementioned object, an antimony-doped silicon single crystal wafer, which has a crystal defect density at a surface of the antimony-doped silicon single crystal wafer of 0.1 number/cm2 or less.
Such an antimony-doped silicon single crystal wafer having a crystal defect density at a surface of the antimony-doped silicon single crystal wafer of 0.1 number/cm2 or less is a silicon single crystal wafer in which the density of grown-in defects at the wafer surface is suppressed to an extremely lower level compared with conventional antimony-doped silicon single crystal wafers. Therefore, by using such an antimony-doped silicon single crystal wafer as a substrate wafer for producing an epitaxial wafer, an epitaxial silicon single crystal wafer having an epitaxial layer of good quality can be obtained.
The present invention also provides an antimony-doped silicon single crystal wafer, which has an oxide precipitate or oxidation induced stacking fault density of 1xc3x97109 number/cm3 or higher after a precipitation heat treatment of the antimony-doped silicon single crystal wafer.
Such an antimony-doped silicon single crystal wafer having an oxide precipitate or oxidation induced stacking fault density of 1xc3x97109 number/cm3 or higher after a precipitation heat treatment of the antimony-doped silicon single crystal wafer exhibits extremely high gettering ability. Therefore, it can be a silicon single crystal wafer of extremely low heavy metal impurity density in the wafer surface layer. Thus, by using such an antimony-doped silicon single crystal wafer as a substrate wafer for producing an epitaxial wafer, an epitaxial silicon single crystal wafer having an epitaxial layer of good quality can be obtained.
The present invention further provides an antimony-doped silicon single crystal wafer, which has a crystal defect density at a surface of the antimony-doped silicon single crystal wafer of 0.1 number/cm2 or less, and an oxide precipitate or oxidation induced stacking fault density of 1xc3x97109 number/cm3 or higher after a precipitation heat treatment.
Such an antimony-doped silicon single crystal wafer having a crystal defect density on a surface of the antimony-doped silicon single crystal wafer of 0.1 number/cm2 or less and an oxide precipitate or oxidation induced stacking fault density of 1xc3x97109 number/cm3 or higher after a precipitation heat treatment is a silicon single crystal wafer in which the density of grown-in defects on the wafer surface is suppressed to an extremely lower level compared with conventional antimony-doped silicon single crystal wafers. In addition, since it exhibits extremely high gettering ability, it can be a silicon single crystal wafer having an extremely low heavy metal impurity density in the wafer surface layer. Therefore, by using such an antimony-doped silicon single crystal wafer as a substrate wafer for producing an epitaxial wafer, an epitaxial silicon single crystal wafer having an epitaxial layer of extremely good quality can be obtained.
The present invention also provides an antimony-doped silicon single crystal wafer, which is obtained by slicing a silicon single crystal ingot grown by the Czochralski method with nitrogen doping.
Such an antimony-doped silicon single crystal wafer obtained by slicing a silicon single crystal ingot grown by the Czochralski method with nitrogen doping can have an extremely reduced density of large-size grown-in defects on the wafer surface due to the action of nitrogen. Moreover, oxygen precipitation is enhanced by the presence of nitrogen in a bulk portion of the wafer. Thus, the wafer can have high gettering effect after a heat treatment of short period of time even though it has such a relatively low substrate oxygen concentration as will not cause problems such as deformation of the wafer or reduction of wafer strength.
Furthermore, if such an antimony-doped silicon single crystal wafer is used as a substrate wafer for producing an epitaxial wafer, high gettering effect can be obtained by a heat treatment of short period of time, and heavy metal impurity concentration of the epitaxial layer can extremely be reduced, because the large-size grown-in defects on the wafer substrate surface are few, and hence adverse influence on the epitaxial layer becomes extremely small. Therefore, it can enable production of an epitaxial silicon single crystal wafer having an epitaxial layer of extremely high quality with high productivity.
Furthermore, the aforementioned antimony-doped silicon single crystal wafer preferably has an oxygen concentration of 20 ppma or less according to the standard of JEIDA (Japan Electronic Industry Development Association).
Such a low or medium oxygen concentration of 20 ppma or less reduces the risk of deformation of the wafer or reduction of wafer strength. In addition, it can inhibit formation of crystal defects in the antimony-doped silicon single crystal wafer, and prevent formation of oxide precipitates in the surface layer of the wafer. Therefore, when an epitaxial layer is formed on the wafer surface, the crystallinity of the epitaxial layer is not adversely affected. On the other hand, because oxygen precipitation is promoted by the existence of nitrogen in a bulk portion, sufficient gettering effect can be obtained in spite of such a low or medium oxygen concentration.
The present invention also provides, in order to achieve the aforementioned object, a phosphorus-doped silicon single crystal wafer, which has an oxygen concentration in the phosphorus-doped silicon single crystal wafer of 18 ppma or less according to the standard of JEIDA (Japan Electronic Industry Development Association), and an oxide precipitate or oxidation induced stacking fault density of 1xc3x97109 number/cm3 or higher after a precipitation heat treatment.
Such a phosphorus-doped silicon single crystal wafer having an oxide precipitate or oxidation induced stacking fault density of 1xc3x97109 number/cm3 or higher after a precipitation heat treatment in spite of the medium or low oxygen concentration in the phosphorus-doped silicon single crystal wafer of 18 ppma or less, in which oxygen precipitation is likely to occur, can have high gettering ability against heavy metal impurities such as those of copper and nickel even with a heat treatment of a short period of time. In addition, because of the low oxygen concentration in the wafer, deformation of the wafer or insufficient wafer strength can be prevented.
Furthermore, by using such a phosphorus-doped silicon single crystal wafer as a substrate wafer for producing an epitaxial wafer, an epitaxial silicon single crystal wafer with high gettering effect and a very low heavy metal impurity concentration can be obtained with high productivity by a heat treatment of a short period of time without generating harmful defects in the epitaxial layer caused by out-diffusion of oxygen impurities.
The present invention also provides a phosphorus-doped silicon single crystal wafer, which is obtained by slicing a silicon single crystal ingot grown by the Czochralski method with nitrogen doping.
In such a phosphorus-doped silicon single crystal wafer obtained by slicing a silicon single crystal ingot grown by the Czochralski method with nitrogen doping, oxygen precipitation is enhanced by the presence of nitrogen in a bulk portion of the wafer. Thus, the wafer can have high gettering effect with a heat treatment of a short period of time even though it has such a relatively low substrate oxygen concentration as will not cause problems such as deformation of the wafer or reduction of wafer strength.
Furthermore, if such a phosphorus-doped silicon single crystal wafer is used as a substrate wafer for producing an epitaxial wafer, an epitaxial silicon single crystal wafer of high gettering effect and an extremely low heavy metal impurity concentration can be obtained with high productivity by a heat treatment of a short period of time.
Furthermore, the aforementioned phosphorus-doped silicon single crystal wafer preferably has an oxygen concentration of 18 ppma or less.
Such a low or medium oxygen concentration of 18 ppma or less further reduces the risk of deformation of the wafer or reduction of wafer strength. In addition, it can inhibit formation of crystal defects in the phosphorus-doped silicon single crystal wafer, and prevent formation of oxide precipitates in the surface layer of the wafer. Therefore, when an epitaxial layer is formed on the wafer surface, the crystallinity of the epitaxial layer is not adversely affected. On the other hand, because oxygen precipitation is promoted by the existence of nitrogen in a bulk portion, sufficient gettering effect can be obtained in spite of such a low oxygen concentration.
When a silicon single crystal is grown with nitrogen doping, it is preferred that the doping should be performed so that the nitrogen concentration in the aforementioned silicon single crystal wafer should be 1xc3x971010 to 5xc3x971015 atoms/cm3.
This is because the concentration is desirably 1xc3x971010 atoms/cm3 or higher in order to suppress the formation of large-size grown-in defects in the silicon wafer and to obtain an effect for sufficiently promoting oxygen precipitation, and it is preferably 5xc3x971015 atoms/cm3 or less in order not to inhibit single crystallization of the silicon single crystal by the Czochralski method.
Furthermore, the aforementioned silicon single crystal wafer is preferably one subjected to a heat treatment at a temperature of from 900xc2x0 C. to the melting point of silicon.
In such a silicon single crystal wafer subjected to a heat treatment at a temperature of from 900xc2x0 C. to the melting point of silicon, nitrogen and oxygen in the surface layer of the silicon single crystal wafer are out-diffused, and hence crystal defects at the wafer surface will become very few. Moreover, the subsequent precipitation is not inhibited by dissolution of precipitation nuclei during a heat treatment at a high temperature such as one for the formation of epitaxial layer, and a wafer exhibiting sufficient gettering effect is obtained.
The present invention further provides an epitaxial silicon single crystal wafer, wherein an epitaxial layer is formed on a surface of the silicon single crystal wafer of the present invention.
Such an epitaxial silicon single crystal wafer having an epitaxial layer formed on the surface of the silicon single crystal wafer of the present invention is free from the problem of auto doping, and hence it can have an epitaxial layer of high quality with a desired resistivity. In addition, it can be an epitaxial silicon single crystal wafer that can be produced with high productivity and have high gettering ability against heavy metal impurities such as those of copper and nickel and an extremely low heavy metal concentration in spite of such a suppressed substrate oxygen concentration as will not cause problems such as deformation of the wafer and reduction of wafer strength.
The present invention also provides a method for producing a boron-doped silicon single crystal wafer having a resistivity of from 10 mxcexa9xc2x7cm to 100 mxcexa9xc2x7cm , which comprises growing a silicon single crystal ingot doped with boron and nitrogen by the Czochralski method, and slicing the silicon single crystal ingot into a silicon single crystal wafer.
When a boron-doped silicon single crystal wafer having a resistivity of from 10 mxcexa9xc2x7cm to 100 mxcexa9xc2x7cm is produced by growing a silicon single crystal ingot doped with boron and nitrogen by the Czochralski method, and slicing the silicon single crystal ingot into a silicon single crystal wafer as described above, oxygen precipitation is enhanced by the presence of nitrogen in a bulk portion of the wafer. Therefore, there can be produced a boron-doped silicon single crystal wafer that has high gettering effect even though it has such a substrate oxygen concentration as will not cause problems such as deformation of the wafer or reduced wafer strength.
Furthermore, if a boron-doped silicon single crystal wafer produced by such a method is used as a substrate wafer for producing an epitaxial wafer, incorporation of impurities into an epitaxial layer due to the auto doping can be prevented, and hence an epitaxial silicon single crystal wafer of high gettering effect and an extremely low heavy metal impurity concentration can be obtained with high productivity.
In the aforementioned method, the oxygen concentration in the single crystal ingot is preferably controlled to be 16 ppma or less.
With such an oxygen concentration, sufficient gettering effect can be obtained without adversely affecting crystallinity of the epitaxial layer.
The present invention also provides a method for producing an antimony-doped silicon single crystal wafer, which comprises growing a silicon single crystal ingot doped with antimony and nitrogen by the Czochralski method, and slicing the silicon single crystal ingot into a silicon single crystal wafer.
By producing an antimony-doped silicon single crystal wafer by growing a silicon single crystal ingot doped with antimony and nitrogen by the Czochralski method, and slicing the silicon single crystal ingot into a silicon single crystal wafer as described above, the density of grown-in defects at the surface of the wafer is markedly reduced by the action of nitrogen. Moreover, oxygen precipitation is enhanced by the presence of nitrogen in a bulk portion of the wafer. Thus, there can be produced, with a heat treatment of short period of time, an antimony-doped silicon single crystal wafer that has high gettering effect even though it has such a relatively low substrate oxygen concentration as will not cause problems such as deformation of the wafer or reduced wafer strength.
Furthermore, if such an antimony-doped silicon single crystal wafer as produced by the aforementioned method is used as a substrate wafer for producing an epitaxial wafer, bad influence of the large-size grown-in defects at the substrate wafer surface on the epitaxial layer becomes extremely small, hence high gettering effect can be obtained by a heat treatment of a short period of time and heavy metal impurity concentration of the epitaxial layer can extremely be reduced. Therefore, it can enable production of an epitaxial silicon single crystal wafer having an epitaxial layer of extremely high quality with high productivity.
In the aforementioned method, the oxygen concentration in the single crystal ingot is preferably controlled to be 20 ppma or less.
With such an oxygen concentration, sufficient gettering effect can be obtained without adversely affecting crystallinity of the epitaxial layer.
The present invention also provides a method for producing a phosphorus-doped silicon single crystal wafer, which comprises growing a silicon single crystal ingot doped with phosphorus and nitrogen by the Czochralski method, and slicing the silicon single crystal ingot into a silicon single crystal wafer.
When a phosphorus-doped silicon single crystal wafer is produced by growing a silicon single crystal ingot doped with phosphorus and nitrogen by the Czochralski method, and slicing the silicon single crystal ingot into a silicon single crystal wafer as described above, oxygen precipitation is enhanced by the presence of nitrogen in a bulk portion of the wafer. Therefore, there can be produced, with a heat treatment of a short period of time, a phosphorus-doped silicon single crystal wafer, in which oxygen precipitation is relatively unlikely to occur, that can have high gettering effect even though it has such a substrate oxygen concentration as will not cause problems such as deformation of the wafer or reduction of wafer strength.
Furthermore, if a phosphorus-doped silicon single crystal wafer produced by such a method is used as a substrate wafer for producing an epitaxial wafer, an epitaxial silicon single crystal wafer having an epitaxial layer of high quality having high gettering effect and an extremely low heavy metal impurity concentration can be obtained by a heat treatment of a short period of time with high productivity.
In the aforementioned method, the oxygen concentration in the single crystal ingot is preferably controlled to be 18 ppma or less.
With such an oxygen concentration, sufficient gettering effect can be obtained without adversely affecting crystallinity of the epitaxial layer.
Further, when a silicon single crystal doped with nitrogen is grown by the Czochralski method in the aforementioned method, it is preferred that the nitrogen doping should be performed so that the nitrogen concentration in the aforementioned single crystal ingot should be 1xc3x971010 to 5xc3x971015 atoms/cm3, and the silicon single crystal wafer is preferably subjected to a heat treatment at a temperature of from 900xc2x0 C. to the melting point of silicon.
By producing a silicon single crystal wafer as described above, there can be produced a silicon single crystal wafer having further higher gettering ability, few surface defects and other various excellent characteristics, which is suitable for a substrate wafer on which epitaxial growth is performed.
The present invention also provides a method for producing an epitaxial silicon single crystal wafer, which comprises producing a silicon single crystal wafer by the method for producing a silicon single crystal wafer of the present invention, and forming an epitaxial layer on a surface of the silicon single crystal wafer.
If an epitaxial silicon single crystal wafer is produced by producing a silicon single crystal wafer by the method for producing a silicon single crystal wafer of the present invention, and forming an epitaxial layer on a surface of the silicon single crystal wafer as described above, influence of grown-in defects at the substrate wafer surface on the epitaxial layer becomes extremely small, and the heavy metal impurity concentration in the epitaxial layer can be extremely reduced because high gettering effect against heavy metals can be imparted by a heat treatment of a short period of time even though the substrate oxygen concentration is suppressed in order not to cause problems such as deformation of the wafer and reduction of wafer strength. Therefore, an epitaxial silicon single crystal wafer having an epitaxial layer of high quality can be produced with high productivity.
As described above, a silicon wafer doped with nitrogen is used as a substrate for an epitaxial silicon single crystal wafer in the present invention. This enables easy production of silicon single crystal wafers of high quality, in which oxygen precipitation readily occur and high gettering effect is exerted, even for a highly boron-doped silicon single crystal wafer of a low oxygen concentration as well as antimony-doped silicon single crystal wafer and phosphorus-doped silicon single crystal wafer in which oxygen precipitation is hard to occur. Furthermore, when epitaxial growth is performed on a surface of the wafer, an epitaxial silicon single crystal wafer of high quality with a low defect density and a low heavy metal impurity concentration in the epitaxial layer can easily be produced with high productivity.